Thermostat stuck open?

Hi has anyone had any issues with there thermostat? It's getting cold here in Michigan and my truck is taking a little longer to reach operating temperature and the heat is blowing cooler air. It is also running a little cooler than it normally does. The gauge is about 3/8 of the way up. Also coolant level is where it always is. Had a coolant flush from the Toyota dealership about 5K ago. Thinking maybe my thermostat is stuck open?

 

Here's what I found:
If you notice that your thermostat gauge stays on the “C” even after the engine has time to heat up, you may have a broken thermostat. If the thermostat can’t signal to the car that the engine is warm, the coolant won’t be sent over to provide heat to your heater core and the air will stay cool. Thermostats are a relatively easy and inexpensive fix, so installing a new one can get your heater working again quickly.

From what you're saying this sounds like it could line up. If your temp gauge is barely moving I'd be looking into the thermostat first as it's fairly cheap. The part I found is about $50 from Toyota. I'm sure you could find it cheaper on eBay.

 

Have you felt the hoses leading to the heater core to see how hot they are (or aren't)?

 

Thats kind of what I was thinking. what I was looking at. I'd rather pay a little more and get an oem. Thanks!

 

I have not yet I was going to check after my 15 minute drive home from work.

 

Feel the radiator core 5 or 10 minutes after a cold start up and see if it feels warm. If it does, the thermostat is probably bad. Not exactly scientific data, but a probable clue.

Also, you can use an infrared thermometer pointed at the thermostat housing to get real world numbers. Harbor Freight has them cheap and you can use them for other cool things. I use mine to measure my forehead temperature to see if I've got covid.

 

Coolant always flows through the heater core, regardless of it's temperature. The quickest way to get heat out of the heater is by starting out with the fan OFF and driving for a few miles until the temperature gauge gets part way up. Then put the fan on low, MODE to HEAT (not defrost, which runs the A/C) and RECIRC mode. If you start out cold and run the fan on HI it will take a long time to warm up because the heater is removing heat at a high rate, plus fast moving air feels cold.